Contemporary zoom lens power configurations normally have an optical axis and are commonly based on a negative (−) and positive (+) combination of lens groups to provide zooming which are usually, but not always, preceded by a positive (+) lens group which provides focusing and following those lens groups a positive (+) lens group is employed to converge the radiation to a sensor in image space.
This arrangement of negative and positive optical powers in the zooming portion has a possible disadvantage of making the first positive lens group large in diameter, weight and cost especially where wide fields of view and focusing is required and in particular where focus breathing is controlled during focusing.
This arrangement may cause the first positive lens group to typically require the use of several lens elements, perhaps even up to 7 lens elements or more, which may contribute about 50% of the weight of the entire optical system and whose optical materials may contribute about 50% of the cost of all the optical materials employed in the entire optical system.
Thus, it is highly desirable to minimize the diameter, weight and corresponding cost of the first lens group of the optical system.